TL;DR: SS-31 (elamipretide) is a mitochondria-targeted peptide that binds a fat molecule inside the mitochondrial membrane, aiming to keep the cell's power-generating machinery working properly and cut down on the damaging by-products it produces under stress. Unlike most peptides on this site, it has gone through multiple real Phase 2 and Phase 3 human trials, in Barth syndrome, primary mitochondrial myopathy and a form of age-related vision loss. Despite that unusually deep trial record, it has not been approved by any regulator, and its largest Phase 3 trial for muscle disease did not meet its main goal. It is a genuine case of strong lab-level science that has not yet translated into a proven human treatment.
What is SS-31?
SS-31, known clinically as Elamipretide (also referenced in earlier literature as Bendavia or MTP-131), is a synthetic tetrapeptide belonging to the Szeto-Schiller family of mitochondria-targeted compounds, named after its originators Hazel H. Szeto and Peter Schiller. Unlike growth hormone secretagogue peptides, SS-31 is built on an alternating aromatic-cationic amino acid motif that allows it to concentrate selectively in the inner mitochondrial membrane, where it binds cardiolipin — a phospholipid found almost exclusively in that membrane and essential to maintaining the folded cristae structure that supports efficient electron transport chain (ETC) function.
Elamipretide has since been developed clinically by Stealth BioTherapeutics and carries one of the more extensive real human trial programmes among mitochondria-targeted research peptides, spanning Barth syndrome, primary mitochondrial myopathy, and dry age-related macular degeneration (dry AMD). Despite this substantial clinical investment across multiple Phase 2 and Phase 3 trials, it is important to state plainly that Elamipretide has not achieved FDA or EMA approval for any indication, and several of its late-stage trials did not meet their primary endpoints. This guide is for educational and research purposes only. Not medical advice.
How strong is the evidence?
| Evidence Type |
Status |
| Human RCT |
✔ |
| Observational |
✔ |
| Animal Studies |
✔ |
| In Vitro |
✔ |
| Regulatory Approval |
✗ |
Multiple real Phase 2/3 human randomised controlled trials have been conducted, alongside observational extension studies, animal models, and in vitro cardiolipin-binding work. No regulatory body has approved Elamipretide for any indication to date, despite this unusually deep trial record for a research peptide.
How does SS-31 work?
SS-31/Elamipretide works fundamentally differently from GH-secretagogue peptides such as Ipamorelin or CJC-1295 — it does not act on a cell-surface receptor to trigger a hormonal cascade. Instead, its aromatic-cationic structure allows it to accumulate in mitochondria and bind directly to cardiolipin on the inner mitochondrial membrane. This interaction is thought to stabilise the folded cristae architecture of the membrane, which in turn supports more efficient assembly and function of electron transport chain complexes.
By protecting cristae structure and ETC efficiency, research models suggest SS-31 can reduce electron leakage and the resulting production of reactive oxygen species (ROS), while supporting more consistent ATP synthesis. This positions the compound as a mitochondria-targeted bioenergetics and antioxidant candidate rather than a hormone-modulating peptide, which is why its research programme centres on conditions with a clear mitochondrial or oxidative-stress component — muscle disease, cardiac tissue, and retinal degeneration — rather than growth, body composition, or metabolic peptide-typical endpoints.
What has SS-31 been studied for?
Mitochondrial Bioenergetics & Cristae Structure
The foundational body of SS-31 research is preclinical and in vitro work demonstrating cardiolipin binding, cristae stabilisation, and improved electron transport chain coupling in isolated mitochondria and cell models. These studies form the mechanistic basis for all later clinical trial programmes and consistently show reduced ROS output alongside preserved ATP-generating capacity under stress conditions.
Barth Syndrome Research (TAZPOWER Trial)
The TAZPOWER trial (NCT02653548) investigated Elamipretide in patients with Barth syndrome, a rare genetic mitochondrial cardiomyopathy. The trial reported improvements in 6-minute walk test distance and some functional and patient-reported measures. However, results were mixed and nuanced — the trial did not cleanly meet all of its co-primary endpoints, and this should be represented honestly rather than as an unambiguous success.
Primary Mitochondrial Myopathy Research (MMPOWER / MMPOWER-3)
The MMPOWER and MMPOWER-3 trials examined Elamipretide in primary mitochondrial myopathy. MMPOWER-3, a Phase 3 trial, is a notable negative result in the peptide's research record: it did not meet its primary endpoint of 6-minute walk distance versus placebo. This is an important and real finding that should not be omitted — it represents one of the clearest signals that, despite strong preclinical rationale, clinical efficacy in this population was not demonstrated at the Phase 3 level.
Ophthalmic Research in Dry AMD
The ReCLAIM and ReCLAIM-2 trials explored intravitreal and subretinal Elamipretide in dry age-related macular degeneration, specifically geographic atrophy. Results were mixed — some anatomical benefit signals were reported, but these were not uniformly matched by functional visual outcome improvements. Elamipretide has also appeared in ophthalmology literature discussing Leber hereditary optic neuropathy, though this remains exploratory.
What did the studies actually find?
What has SS-31 been studied alongside?
- SS-31 + MOTS-c → Research rationale: Both are mitochondria-associated peptides; researchers have explored combining a cardiolipin-stabilising compound (SS-31) with a mitochondrial-derived peptide implicated in cellular energy signalling (MOTS-c) to examine complementary effects on cellular bioenergetics.
- SS-31 + antioxidant compounds (e.g., CoQ10 analogues) → Research rationale: Investigated in preclinical settings for combined mitochondrial-protective and ROS-scavenging effects, given SS-31's role in reducing electron transport chain leakage.
⚠️ Stack combinations listed for research reference only. Not safety or efficacy guidance.
Why there are no doses on this page
This site does not publish doses, durations or frequencies for any compound. Published research protocols for this compound vary considerably between studies in design, intensity and duration. Those details are not something to copy from a fitness website — anyone researching this compound should read the primary literature directly and talk to a doctor who knows their bloods.
Figures above are drawn from published trial-context dosing (TAZPOWER, MMPOWER, MMPOWER-3, ReCLAIM, ReCLAIM-2) and are presented purely as historical trial reference, not as a recommendation.
What side effects were reported?
- Injection site reactions / erythema (the most commonly reported adverse event across chronic subcutaneous trials)
- Mild gastrointestinal discomfort (reported in some trial participants)
- Transient headache (infrequent)
Across the TAZPOWER, MMPOWER, and ReCLAIM trial programmes, Elamipretide was generally reported as well-tolerated with a relatively clean safety profile. No major severe adverse event pattern emerged in the trials cited, though injection site reactions were a consistent and common finding.
SS-31 at a glance
- CAS Number
- 736992-21-5
- Molecular Formula
- C40H60N10O7
- Molecular Weight
- Approximately 807.98 g/mol (free base; salt forms vary)
- Half-Life
- Short (minutes); typically administered by daily subcutaneous injection in trials
- Synonyms
- Elamipretide, Bendavia, MTP-131
- Research Classification
- Mitochondria-Targeted Tetrapeptide, Cardiolipin-Binding Compound, Szeto-Schiller (SS) Peptide
The research this page cites
- Szeto HH et al. 2014 — First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. — British Journal of Pharmacology — [Review / Mechanism]
- Thompson WR et al. 2024 — Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER. — Genetics in medicine — [Human RCT]
- Karaa A et al. 2023 — Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. — Neurology — [Human RCT]
- Ehlers JP et al. 2024 — ReCLAIM-2: A Randomized Phase II Clinical Trial Evaluating Elamipretide in Age-related Macular Degeneration, Geographic Atrophy Growth, Visual Function, and Ellipsoid Zone Preservation. — Ophthalmology Science — [Human RCT]
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